1. Field of the Invention
This invention relates to seatbelt retractors for motor vehicles and more particularly to seatbelt retractors for motor vehicles which only prevent extension of the seatbelt during motor vehicle emergencies such as collisions, etc.
2. Prior Art
In prior art there are seatbelt retractors which prevent the extension of the seatbelt only during motor vehicle emergencies. During a motor vehicle emergency in such prior art seatbelt retractors, an acceleration sensing member causes a pawl to dip such that the pawl engages with a locking gear attached to a seatbelt retracting shaft thereby preventing the rotation of the retracting shaft in the direction of seatbelt extension. Since the rotation of the retracting shaft in the direction of seat belt extension is thus checked, the body of the vehicle passenger wearing the seatbelt is restrained such that the passenger is not thrown in the direction of the collision during the vehicle emergency. Accordingly, the safety of the passenger is assured.
Further, in this type of a seatbelt retractor system, however, the tips of the pawl sometimes strike the tips of the teeth of the locking gear during the initial stages of engagement between the pawl and the locking gear. This phenomenon is known as "tip-to-tip condition" and is an extremely dangerous condition for a person wearing the seatbelt. This condition is known to be a contributing cause of severe injury during accidents. Specifically, the passenger is accelerated in the direction of the collision during a vehicle emergency thereby causing the retracting shaft to rotate abruptly in the direction of seatbelt extension so that the pawl which has struck the tips of the teeth of the locking gear is kicked back considerably by the locking gears. Accordingly, a relatively long period of time is required before the pawl is securely engaged with the locking gears. During this relatively long period of time, the seatbelt extends to a considerable extent so that the passenger is insufficiently restrained and is therefore placed in an extremely dangerous situation.